Sound is one of the main senses in the human body. We perceive sound through a series of processes that occur in the body. The ears are the external organs for hearing. They are located at the openings of the ear canal. This canal leads to the tympanum which is a membrane separating the outer and inner ear. This membrane vibrates a set of bones in the inner ear which produce a sound that can be picked up by the nerve endings in the ear. This sound is transmitted to the brain through the nerves responsible for hearing. The process of hearing can be affected by a failure in any one of these stages of the process. Hearing loss can be caused by a physical impairment such as the formation of wax deposits in the ear canal that become thick enough to block hearing.
Hearing loss may also be caused by damage to the tympanum that could be the result of excessively loud noises or being exposed to some sort of an explosion which causes a sudden wave of energy to hit the membrane, damaging it. Internal infections may also cause hearing loss which can be temporary, if it is restricted to an inflammation or permanent, if some irreparable damage has occurred to the delicate structures within the ear. Such an infection might also cause balance and motor problems because the balance of the body is managed by the canals within the ear. Complete deafness is a condition that affects many people across the world. There are environmental and genetic causes that have been linked to complete hearing loss. Such people are able to communicate using sign language but have to be extremely careful, especially while using transport or walking on the streets.
A popular test to measure a person's hearing ability and therefore their ability to communicate is the hearing in noise test or popularly known as HINT. During this test, a person is made to listen to a set of sentences with no background noise. The person is made to repeat or note these sentences down to confirm that he or she has heard the sentences properly. The subject is then made to hear some new sentences with a high amount of background noise. A deficiency in the hearing system of the person will make it difficult or impossible for him or her to hear the sentences in the noisy environment. The HINT has helped to establish the importance of directional hearing as well.